Imagine a string of Christmas tree lights – one long cable with many bulbs plugged in. Sensor chaining is a similar concept: one long cable stretching down a data center server aisle with multiple probes attached. Each probe monitors temperature and humidity and, because they are spaced at regular intervals throughout the data hall, conditions are maintained at optimal levels all the way along the chain.

The need for modularity

The needs of colocation data centers, where space is rented out to multiple tenant companies, differ from those of hyperscale data centers with a single owner-occupier. While both require optimal atmospheric conditions to protect sensitive equipment and a reliable monitoring solution to control them, colocation data centers ideally need a modular setup to cope with changing customer requirements and shifting operational layouts.

What is sensor chaining?

Sensor chaining, also known as daisy chaining, is the perfect solution for colocation data centers. A sensor chaining solution consists of a cable running from a control panel down two data center aisles, with temperature and humidity probes attached via three-way splitters along the length. A typical data center might have a 60-meter run of sensors, but the solution could extend up to hundreds of meters. In optimal conditions the solution would work for much greater distances too.

In a sensor chain, only one power supply is needed to run hundreds of probes from a single control panel, and as it is a plug-and-play solution there is flexibility to add more racks or change the data center layout at any time – you just remove the sensors and reuse them elsewhere. The plug-and-play functionality also means probes can be easily switched out for calibration whenever needed, ensuring long-term accuracy and reliability with no downtime.

The traceable multi-point calibrated Vaisala HUMICAP® Humidity and Temperature Probe HMP113 is the ideal probe for sensor chaining and has proven itself in many data center installations. A stainless-steel model, the Vaisala HUMICAP® Humidity and Temperature Probe HMP110, is also available.

Quick and easy to install – and change

The Vaisala sensor chain solution can be installed quickly and easily by a technician or facility manager with no need for a system integrator. With each probe taking just seconds to attach and no hard wiring, installation time and cost are significantly lower than traditional solutions.

A typical fixed sensor solution for data centers can be inherently wasteful. If your needs and layout change – perhaps a new client is moving into the data center, or you need to expand – it’s not uncommon to replace all the sensors at the same time, which can number in the thousands. With an interchangeable sensor-chaining solution all your sensors can be reused indefinitely throughout their lifetime, improving the sustainability of the data center. Simply switch the probes out and plug them into your new layout.

Flexibility, reliability, and accuracy all in one solution

The sensor chaining solution isn’t just flexible after it’s been installed – it’s a flexible solution in design too. As well as the HMP113 and HMP110, there is also the hard-wired Vaisala Humidity and Temperature Transmitter HMW110, which has an optional integrated display. A daisy-chained HMW110 provides a more accurate reading than wall-mounted sensors as there is free airflow for 360° around its probe. You could choose to have a display unit at the beginning, middle, and end of your sensor chain, use display units throughout or have no displays at all, depending on your needs.

This flexibility extends to the communication protocol too. The sensors typically utilize a Modbus protocol, but if you need a 4-20mA connection it is still possible to have a modular solution with a cable plugged straight into the transmitter. The sensors have a magnetic bracket on the back so they can be easily attached to the side of a metal rack, saving time on wiring and installation and giving you the benefits of a daisy-chained solution. When you consider it can take 30–40 min installation time per hard-wired device and you might have a couple of thousand on site, the time saved with a magnetic plug-and-play solution is significant.

The sensor-chaining solution has proved extremely reliable, but in the very unlikely event there is cable damage, the building management system will generate an alert so the relevant sensors can be unplugged and replaced. Redundancy can also be built into the system, with each cable run covering two aisles – this means if a cable isn’t working then readings are picked up from the second bus.

Best-in-class accuracy and 24/7 support

Vaisala sensors are best-in-class in terms of accuracy and measurement stability, giving them a longer, more reliable lifetime. A sensor-chaining setup makes them interchangeable as your needs change, adding the essential benefit of flexibility while increasing the sustainability and cost-effectiveness of the solution.

Regular calibration will keep your sensors performing reliably and as the system is plug-and-play, this doesn’t require any downtime – simply swap sensors out when needed. Vaisala also offers a field calibration service where our experts can come to your data center to calibrate your equipment on site. We also offer 24/7 technical support with local experts, and monitoring solutions for liquid cooling applications, leak detection, and water-in-oil measurement.

Get in touch for help to identify the right sensor-chaining option for your specific needs, or let us work with you to develop a bespoke monitoring solution.